1. Field of the Invention
This invention relates to the field of grease-hood and grease-filter apparatus, particularly for use in restaurants.
2. Description of Prior Art
For a great number of years, food was cooked in and around fireplaces, stoves, etc., and the smoke was allowed to pass up the chimney by pure convective action. However, smoke often escaped to the room causing deposition of grease on various surfaces of the wall, ceiling, etc. Furthermore, there was much grease and charred material collected in the chimney, a potent fire hazard.
In relatively modern times, it was determined that the public welfare would be improved by requiring restaurants to install suction fans which would draw large volumes of air up the chimney. The idea was to get the smoke and grease up the chimney so fast, and throw it out into the air so far, that it would not cause trouble. These systems were failures, for many reasons, including: (a) the grease collected in and around the chimney, on the roof, etc., with consequent fire and sanitation problems, (b) large amounts of heated or air-conditioned air were drawn from the restaurant and passed up the chimney, with consequent extreme wastage of fuel and also with much discomfort (caused by strong drafts) to the patrons and cooks in the restaurant, (c) the smoke sometimes bounced back in the cook's face, despite the strong drafts, creating discomfort to him or her, and (d) the food on the stove was cooled excessively by the rapid air flow.
The next step in the evolutionary process was to provide grease filters (in addition to the high-volume forced-air flows) relatively close to the cooking space. These also were failures because they did (unless prohibitively expensive and complicated) a poor job of filtering -- so that grease still lined the chimney and collected on the roof. There was therefore a distinct problem whereby the chimney required cleaning (often by independent service companies) several times per year. The filters not only did an adequate job of filtering, but they tended to increase the problem of smoke bouncing or billowing back into the cook's face.
The above problems were solved by the advent of convective-flow and vortex apparatus described in U.S. Pat. No. 3,664,255 and in Pat. No. 3,952,640 and U.S. Pat. No. 3,943,836, (which apparatus, except for some forms of said U.S. Pat. No. 3,952,640, have been on the market more than one year prior to the filing date of the present application). However, such vortex apparatus has to date only been employed in hoods of the canopy type, wherein the bottom of the hood is spaced so high above the floor that the cook may walk beneath it without bumping his head. The front of the canopy hood overhangs much of the area where the cook stands.
In the canopy structures illustrated in the above-cited patent and patent applications, the maximum horizontal dimension of the vortex was large in comparison to the maximum vertical dimension thereof. Furthermore, the maximum diametral vortex dimension generally perpendicular to the grease-filter means was large in comparison to the maximum diametral vortex dimension in a direction generally parallel thereto.
Canopy hoods (such as those illustrated in the cited patent and patent applications) have been and will continue to be important factors in many restaurants, particularly larger conventional restaurants, but there are many fast-food restaurants and other restaurants wherein the size and expense of the large canopy hoods are not desired. For such restaurants, it is greatly desired that the hoods be sufficiently small that they may be mounted over only the rear portion of the cooking appliance, at a low elevation below that of the head of the cook. Thus, for such last-mentioned types of restaurants, it is extremely important that the front-to-rear dimension of the hood be small, permitting the cook to see the entire cooking surface and to reach the portion thereof without bumping his head on the grease-hood apparatus. It is also important that such hoods be aesthetically satisfactory, and do not have exposed interiors presenting black, sooty aspects to the patrons in the restaurants.
Hood systems of the non-canopy type, and wherein one or more blowers were incorporated, have (insofar as applicant is aware) involved the sucking or blowing (as distinguished from convecting) of large amounts of air at regions far below the hoods. (For example, Jensen U.S. Pat. No. 3,400,649 brings supply air down to the back of the cooking appliance, then blows and sucks it up through the filters, the forced-flow upwardly-directed air being stated to create a venturi effect which draws room air back over the cooking surface.) In numerous other prior-art apparatus, there is an extremely great suction effect whereby room air is sucked in great volumes up the chimney, instead of being substantially balanced by inlet air from a region exterior to the room. Such last-mentioned type of prior-art apparatus is extremely undesirable for numerous reasons including energy wastage, creation of uncomfortable drafts for the customers and cooks, etc.